1. Field of the Invention
The present invention relates to a volume-type hologram resin composition and a surface relief-type hologram resin composition used in, for example, a hologram transfer foil etc., as well as a hologram layer, a hologram transfer foil and a fragile hologram label using thereof.
2. Description of the Related Art
A hologram is that wherein two lights (object light and reference light) having the same wavelength are allowed to interfere with each other and the wave front of the object light is recorded as an interference fringes on a photosensitive material. When a light of the same conditions as those of the original reference light is applied to this hologram, a diffraction phenomenon can occur by an interference fringes to regenerate the same wave front as the original object light. The hologram is classified into some kinds (surface relief-type hologram, volume-type hologram etc.) depending on the recording form of an interference fringes generated by interference of a laser light or a light excellent in coherence.
In recent years, the hologram has been used often in security fields because of its property of difficult reproduction of the same design. In this application, a surface relief-type hologram recording an interference fringes by forming a finely embossed pattern on the surface of a hologram-forming layer is generally used. However, due to distribution of holography technology and upgrading of forgery techniques, a surface relief-type hologram is imitated and reproduced sometimes at such a level that its forgery though recognized by specialists cannot recognized at first sight by laymen. Accordingly, when the hologram is used in application to security, countermeasures such as application of decorative techniques used in paper money and bonds to designs on the hologram and combination of such techniques with other printing techniques come to be necessary.
On the other hand, the volume-type hologram is produced by recording an interference fringes generated by interference of light, as bands different in refractive index three-dimensionally in the direction of thickness of a photosensitive material. This volume-type hologram is different in its production method from that of the surface relief-type hologram used widely at present and is completely different in visual effect, thus facilitating judgment of genuineness. Further, production facilities are expensive, and imitation of designs requires design techniques at high levels, and thus production of the hologram for the purpose of forgery is extremely difficult. Accordingly, there is a need for use of the volume-type hologram in application to security.
Though not concerned with hologram, a crime prevention system and an antitheft tag have been extensively developed in recent years wherein a commodity is provided with e.g. an antitheft tag for prevention of theft, and when the commodity is taken out from a store, the presence of the antitheft tag is detected by a detector to generate an alarm (for example, Japanese Patent Application Laid-Open (JP-A) No. 2003-168090, JP-A2001-315464). Mainly, a magnetic material is used in this antitheft tag, and the magnetic material reacts with e.g. an electromagnetic wave of resonant frequency generated by a detector arranged in an entrance of a store, and its signal is detected.
JP-A 2002-279370 proposes a forgery-preventing seal used in credit cards and gift certificates. This forgery-preventing seal has a substrate, a ferromagnetic substance layer and an adhesive layer, and a signal obtained by applying an alternating current magnetic field to a ferromagnetic substance contained in the ferromagnetic substance layer can be analyzed to judge genuineness.
U.S. Pat. No. 5,986,550 owned by Micro Tag Temed Ltd. proposes a method of certification or discrimination by utilizing a range of specific magnetic resonance phenomena. This is a method that involves adding e.g. a certifying substance to a credit card, a commodity or the like to certify and discriminate it by utilizing nuclear magnetic resonance or nuclear quadrupole resonance. Although U.S. Pat. No. 5,986,550 owned by Micro Tag Temed Ltd. discloses a method of certification and discrimination and an apparatus using this method and general application modes, it does not describe in detail some specific modes of the certifying substance application.
A hologram is not described in any of the methods described above.